Wait - it marks itself as 'read' but only if I reply to a topic - so this one is marking itself a read, but the ones in ChitChat and Tennis Talk aren't, because I haven't posted in them, just looked at them.

3. The problem is with the forum index - the forum categories are fine.

4. When I post, it marks the topic as read when I refresh the forum index.

5. If I just look at a post, it doesn't mark as read when I refresh the forum index.

6. HOWEVER, if I go into the forum category directly from the forum index page (i.e. not to a topic, just to the category) and there are no new posts and THEN I return to the forum index, everythin is marked as read.

I posted under a different user name > I saw on the forum index that there was a new post > I went straight to the new reply instead of first going into the relevant forum section > I went back to the forum index by clicking the link-tree and it still said unread.

That is the problem I assume? And if so then I shall simply uninstall the mod, this was a fairly simple procedure in the first place so no lost time.